1. Field of the Invention
The present invention relates to a novel sulfonate and a resist composition using the same used in fine processing of semiconductors.
2. Related Art
Semiconductor microfabrication usually employs a lithography process using a resist composition. In lithography, theoretically, the shorter the exposure wavelength becomes, the higher the resolution can be made, as expressed by Rayleigh's diffraction limit formula. The wavelength of an exposure light source for lithography used in the manufacture of semiconductor devices has been shortened year by year as g line having a wavelength of 436 nm, i line having a wavelength of 365 nm, KrF excimer laser having a wavelength of 248 nm and ArF excimer laser having a wavelength of 193 nm. F2 excimer laser having a wavelength of 157 nm seems to be promising for the next-generation exposure light source. As the exposure light source of the subsequent generation, soft X ray (EUV) having a wavelength of 13 nm or shorter has been proposed. Further, as a lithography technology of somewhat different type from those above, electron beam lithography is energetically studied.
Since light sources having shorter wavelength than that of g line and i line, such as excimer laser and the like have low illumination, it is necessary to enhance the sensitivity of a resist. Consequently, there are used so-called chemical amplification type resists utilizing the catalytic action of an acid produced from a sulfonium salt and the like by exposure and containing a resin having a group being dissociated by this acid.
However, in conventionally known chemical amplification type resist compositions, there is a problem that line edge roughness occurs by generation of standing wave and the like, namely, smoothness on pattern side walls decreases, and resultantly, uniformity of line width deteriorates.
Though it is effective to use an acid generator including anion of benzenesulfonic acid having at least one ester group for positive type photosensitive compositions having higher photosensitivity and less change on standing after exposure, it is still difficult to combine progress of roughness and progress of pattern shapes.
If such resist composition is used as it is in electron beam lithography, there is the problem that throughput in the production of integrated circuits is low for low sensitivity of the resist composition. Though higher sensitivitization of the resist compositions is desired from the viewpoint above, enhancing sensitivity of a resist generally tends to cause deterioration of resolution and deterioration of smoothness of pattern shapes and pattern sidewalls. The edge roughness of patterns is desired to be low because degree of precision for microfabrication is adversely affected if it is high.